In modern continuous production arrangements, the primary material provides for obtaining thin slabs, which are rolled down in a finishing train and which have a thickness of less than 70 mm, preferably 50 mm. The slabs are separated from a continuous cast piece, which is extruded in a continuous casting machine and have a length corresponding to the coil-weight of the finished hot-rolled wide strip. The casting speed of the continuous casting machines for continuous casting of thin slabs is relatively small, whereas the feed speed of the associated continuous finishing train for hot-rolled wide strip is two to four times faster than the casting speed. Therefore, it is advantageous when two casting machines are associated with a single finishing train, so that slabs are alternatively cut off from two continuously cast pieces from two casting machines and are then transported, respectively, to the finishing train for rolling down. The slab is brought into alignment with the finishing train for producing a hot-rolled wide strip from respective casting machines by two longitudinal/transverse/longitudinal transportation systems, so-called "ferries", and then the slabs are rolled down in the finishing train. In a conventional embodiment of such an arrangement, these two single-strand continuous casting machines are associated each with an equalizing furnace and a "ferry" with two strands being associated with a common holding furnace, which is arranged upstream of the continuous finishing train. Each equalizing furnace has a heating zone, a buffer zone and an accumulating furnace part. In the heating zone, the slabs are brought up to a rolling temperature. The buffer zone is necessary to insure a selective transverse transportation of the slabs from both casting machines into the finishing train in the required transportation time. The accumulating furnace part provides for compensation of a dead time of the finishing train, resulting from, e.g., changing rollers or a disturbance, without the interruption of the production of the continuously cast slabs.
With such arrangement, e.g., the thickness of the slab is 50 mm, the width is 1550 mm, the length is 44 m, the casting speed is 5.5 m/min, and the feed speed of the continuous finishing train for producing a hot-rolled wide strip is 0.29 m/sec. or 17.4 m/min. Here, the ratio of the feed speed to the casting speed is greater than 3.2. With this, the length of the heating zone is about 40 m, the length of the buffer and the accumulator part, taken together, is 105 m, the length of the "ferry" is 49 m, and the length of the holding furnace is 49 m. With these parameters, the length of the furnace installation is about 147 m and, if the length of the "ferry" is included, 194 m, so that the total length, together with the holding furnace, is 245 m. An arrangement of such a length is extremely costly and requires a respectively large surface area. To eliminate this drawback, a novel arrangement concept for the production of steel strip is suggested in European application EP 0 413 169 A1. To reduce the investment expenditure and the requirement in a surface area, as well as for improving the temperature regime, the finishing train is sidewise offset with respect to the output conveyor of the steel strip casting installation, and an intermediate temperature equalizing furnace is arranged sidewise of the equalizing furnace of the casting installation and is offset relative thereto forward in the direction of movement of the seal toward the finishing train. The three equalizing furnaces which extend parallel to each other, are connected by an end face transverse transporting device. The drawback of this arrangement is that the one-time reversal of the transportation direction of the slab results in different dwell time of the front portion of the slab and the rear portion of the slab in the equalizing furnace, and, thereby, in a non-uniform temperature gradient along the slab length. A further drawback of this arrangement concept is that the furnace installation should extend below the casting installation.
An object of the invention is a method of and an apparatus for producing hot-rolled strips or profiles from a continuously cast primary material, which would eliminate the foregoing drawbacks of the known process and arrangement, with comparatively smaller length of the furnace installation, reduced investment expenditure, and a need in a smaller surface area.